QOpenGL入门教程07：旋转

本文将图形旋转起来。

先用OpenGLut常用的glGenBuffers方法

渲染语言

vertice 顶点

#version 330 core

in vec4 aPos;
in vec4 aColor;
out vec4 outColor;
uniform mat4 mvpMatrix;
void main(){
    gl_Position = mvpMatrix * aPos;
    outColor=aColor;
}

fragment 段

#version 330 core

in vec4 outColor;
void main(){
    gl_FragColor = outColor;
}

可以看到段的输入是顶点的输出，也就是说先处理顶点，然后将顶点处理为面。

初始化函数

initializeOpenGLFunctions();//初始化OpenGL上下文内容
glClearColor(0.0f,0.0f,0.0f,1.0f);//将缓冲区清空为RGBA指定的颜色
//使用颜色缓冲区、深度缓冲区、RGBA、alpha支持
glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT|GL_RGBA|GL_ALPHA_BITS);
glEnable(GL_DEPTH_TEST);//使用深度缓冲区测试

program = new QOpenGLShaderProgram;
program->addCacheableShaderFromSourceFile(QOpenGLShader::Vertex,":/resources/vsrc.glsl");
program->addCacheableShaderFromSourceFile(QOpenGLShader::Fragment,":/resources/fsrc.glsl");
program->bindAttributeLocation("aPos",0);
program->bindAttributeLocation("aColor",1);
program->link();//激活Program对象
program->bind();

glGenBuffers(4, &m_vboIds[0]);
GLfloat triangleVertices[] = {
    0.0f, 1.0f, 0.0f,
    -1.0f,-1.0f, 0.0f,
    1.0f,-1.0f, 0.0f,
};
glBindBuffer(GL_ARRAY_BUFFER, m_vboIds[0]);
glBufferData(GL_ARRAY_BUFFER, sizeof(triangleVertices), triangleVertices, GL_STATIC_DRAW);

GLfloat triangleColors[] = {
    1.0f,0.0f,0.0f,
    0.0f,1.0f,0.0f,
    0.0f,0.0f,1.0f
};
glBindBuffer(GL_ARRAY_BUFFER, m_vboIds[1]);
glBufferData(GL_ARRAY_BUFFER, sizeof(triangleColors), triangleColors, GL_STATIC_DRAW);

GLfloat quadVertices[] = {
    1.0f, 1.0f, 0.0f,
   -1.0f, 1.0f, 0.0f,
    1.0f,-1.0f, 0.0f,
   -1.0f,-1.0f, 0.0f
};
glBindBuffer(GL_ARRAY_BUFFER, m_vboIds[2]);
glBufferData(GL_ARRAY_BUFFER, sizeof(quadVertices), quadVertices, GL_STATIC_DRAW);

GLfloat quadColors[] = {
    0.5f,0.5f,1.0f,
    0.5f,0.5f,1.0f,
    0.5f,0.5f,1.0f,
    0.5f,0.5f,1.0f
};
glBindBuffer(GL_ARRAY_BUFFER, m_vboIds[3]);
glBufferData(GL_ARRAY_BUFFER, sizeof(quadColors), quadColors, GL_STATIC_DRAW);

如果渲染语言太多了，就需要将其移至专用文件中，Qt的这种文件格式为glsl，其实叫什么无所谓，内容对就可以。
顶点语言中有两个输入aPos和aColor，分别绑定到顶点位置0和1。
创建4个缓冲区，用于两个图形的顶点坐标和颜色，如果是图片就需要创建纹理Texture。然后绑定数据
GL_STATIC_DRAW表示数据不会修改

绘图函数

先绑定数据

1
2
3

program->bind();
...
program->release();

绘制三角形

m_modelView.setToIdentity();
m_modelView.translate(-1.5f, 0.0f, -6.0f);
m_modelView.rotate(m_rtri,0.0f,1.0f,0.0f);
program->setUniformValue("mvpMatrix", m_projection * m_modelView);
glBindBuffer(GL_ARRAY_BUFFER, m_vboIds[0]);
program->enableAttributeArray(0);
program->setAttributeBuffer(0, GL_FLOAT, 0, 3);
glBindBuffer(GL_ARRAY_BUFFER, m_vboIds[1]);
program->enableAttributeArray(1);
program->setAttributeBuffer(1, GL_FLOAT, 0, 3);
glDrawArrays(GL_TRIANGLES, 0, 3);